1. Field of the Invention
The present invention relates to a needle electrode device with a temperature sensor for medical application, for use in performing high frequency thermocoagulation, ablation, or the like of an affected area by applying a high frequency current to the affected area.
2. Related Background Art
Conventionally, there is already known a needle electrode device for medical application, having a hollow outer needle, which can be pierced into an affected area and is coated with an insulating layer on an outer peripheral surface except at its distal end, and an inner needle to be inserted into the outer needle, so that a high frequency current is supplied to the outer needle through the inner needle in order to apply the high frequency current to an affected area from the distal end of the outer needle, which is not coated with the insulating layer. As this type of needle electrode device, there is disclosed a needle electrode device provided with a temperature sensor at the distal end of the inner needle, so that the temperature of the affected area can be obtained by the temperature sensor (Refer to, for example, U.S. Pat. No. 4,411,266).
The length of the outer needle varies according to the manufacturer, or even if the manufacturer is the same, it varies in some degree from one product to another. Therefore, in order to grasp the temperature of the affected area accurately, it is necessary to adjust the position of the temperature sensor in accordance with the length of the outer needle, in other words, necessary to adapt the inner needle having the temperature sensor at the distal end in such a way as to be freely adjustable in its position in an axial direction relative to the outer needle. Therefore, conventionally there is also known a needle electrode device provided with a coupled tube, which is coupled to the rear end of the outer needle, wherein the rear end of the inner needle is inserted into the coupled tube in such a way as to be freely adjustable in its position in the axial direction.
In this type of needle electrode device, radially threaded holes are formed in the surrounding wall of the coupled tube, locking screws screwed into the threaded holes are pushed against the outer peripheral surface of the rear end of the inner needle so that the rear end of the inner needle can be fixed. In this structure, however, there is a need to loosen and tighten screws each time when adjusting the position of the inner needle. Therefore, this type of needle electrode device has a problem of troublesome operation.